How bad is making mistakes in the lecture slides?

Question

I am giving a lecture in IT (for the first time) to more than 100 students. I refused to use the slides of the previous lecturer and I wanted to make my owns. They take me a lot of effort and I believe that are better than most lecture slides on the same topic.

The lecture includes so many mathematical equations (almost every slide). Because I am making them from scratch, I made already 3 mistakes in the equation (e.g. multiplication instead of addition). I discovered two of them during the lecture I said that it is a mistake. I corrected the mistakes before I uploaded the slides.

the third mistake I did not notice but when I gave an example I used the correct one. In the exercise, the students were claiming that the equation does not give the same result as expected in the exercise (which is graded). I decided to give all the students the full note for that exercise.

My question is how bad to have these mistakes? Should I use the slides of the previous lecturer?

Answer 1

Everyone makes mistakes. Teachers, students, everyone. It isn't terrible that you make them, but it is good, and can be extremely instructive when you correct them.

Your description suggests that you do the right thing here. Proof your slides and make corrections. But also, when mistakes are pointed out in class, not only admit them readily, but work through the correction as needed. If it is just a typing error then it is easy, but logic errors might require more effort.

However, seeing a professor work in real time to solve a problem, rather than just showing prepared stuff is extremely enlightening. Students can get the idea when presentations are perfect that this stuff is supposed to be easy. In fact, it may not be easy and so seeing a solution develop, even seeing false starts and corrections, will give them more confidence in their own work. Especially if they struggle with some of the ideas.

Your students will be evaluating you overall, not just your slides. If you act in a human and humane manner, especially by responding to their needs, you should do fine. But occasionally a student will be unreasonable. Don't worry too much about this.

But perfection in a lecture isn't necessarily the most effect way to teach. That doesn't excuse sloppiness, of course, but consider the overall picture, not just the minute details.

I've had students complement me more often on "lectures" that forced me to work "live" than on those that were very polished. In fact, I once tried to develop a "perfect" description of a hard problem and it left the student baffled. "Where did that come from?"

Be good. Very good. But recognize that you are human, which means being adaptable.

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As to using the previous slides, I have no opinion. They might be good, but they might be too perfect. They might also force you into stilted delivery, which you should avoid.

But as a newcomer to this stuff, you might have conversations with colleagues about your teaching materials and get their feedback. People learn a lot by interacting with students, but it isn't obvious to a new teacher how that all fits together effectively. Some places have more senior instructors visit the classes of new faculty and then give feedback, either formally or informally. There is no real reason why you can't ask a trusted colleague to do that, even if not required. While it might feel risky, it also shows you are trying to improve your craft.

Answer 2

If you are averaging 3 errors/lecture*, that's too much, especially with typed materials. Makes the course hard to follow and creates a real confusion factor of people using the uncorrected materials in error.

Not sure if the solution is to use the previous materials or just tighten up on what you are doing yourself. I suspect there is some way to be better prepared without just using old slides (which may have issues themselves). Wonder if you are somehow trying to be too ambitious. All that said, if you are not so strong on the materials yourself, perhaps using old lecture materials, at least for first run through a class, might be a better course of action. After doing that, you are more knowledgeable about what you want to change and why.

P.s. I hate slides--find blackboard and chalk much more engaging. (But that's off topic.)

*If instead, this was 3 mistakes over an entire course's typed notes, than no biggie.

Answer 3

Well, first up be frank with the students and then give them some freeby decimals on their grade as apology because if they study from the mistakes they will get it wrong in the exams (besides the full note you already gave), and to avoid it, start a mistake hunt.

Give your students ALL the slides and tell them to analyze them and submit the mistakes they find or improvements they can think off, you can do this as part of the grading as some homework project or you can add it as an optional with an extra point or 2 over the final grade, that will be a nice incentive. In the end you can find even more mistakes you didn't noticed, improve the layout or design, have the students study and work, and all resulting into material you can use later on in the future. And your evaluation will be saved.

Answer 4

Making a good slide deck is really, really hard. It is entirely normal that a lecturer needs several years teaching a course to develop the perfect deck.

Consider the purpose of the slides: to give the students the best possible education. If your current deck isn't good enough yet, you should really consider using some of the old deck. There's nothing wrong with using a blend, as long as you give credit to your predecessor. If you really don't like the old deck, you can also look for slide decks for the same topic produced at other universities.

Making good slides is so hard actually, that it's quite normal for a really good slide deck to get used by many grateful lecturers at multiple institutions. For the original creator, this can lead to a lot of name recognition, as someone making a valuable contribution to the community. (Remember to put your name and institution in the footer of your slides.)

Finally, be honest with your students. Encourage them to ask questions, if they think there may be a mistake in a slide. Either in class of privately. Either you find and fix a mistake in your slide (and discover a smart student), or you get to explain to your student why your slide is correct after all (and the student learns something).